This invention relates to the reflex imaging of originals residing on a platen; and, more particularly, to the control of the intensity of the reflex image.
In automatic copying machines, the reflex mode of exposure has proven extremely suitable for use in the copying of many materials, particularly books and other types of bulky items, and has permitted the user the freedom to photocompose information at the input station of the machine. For example, U.S. Pat. No. 3,062,109 discloses a xerographic machine in which the original subject matter to be copied is supported upon a flat horizontal viewing platen and a moving lens system is employed to record an image of the original.
Attempts have been made to make compact copiers which, while occupying less space than previous copiers, nevertheless preserve the advantages found in reflex imaging of a stationary original residing on a platen. These efforts are exemplified in U.S. Pat. Nos. 3,431,053; 3,331,181; and 3,832,057. The first two patents disclose a stationary lens system and moving mirrors arranged to fold the optics in a horizontal direction thus compressing the system vertically. However, this necessitated horizontal expansion and, therefore, a sacrifice in two-dimensional compactness. The third patent successfully achieved a truly compact machine by providing for the horizontal compression of the optical system in addition to the vertical compression.
It has been found desirable, however, to provide further benefits such as the ability to simply, economically, and selectively vary the intensity of the reflex image provided by the aforementioned optical systems in automatic copying machines. For example, it is highly desirable to provide the capacity to compensate for variation in intensity of lamp output and to compensate for different document reflectivities which require different levels of illumination.
In general, liquid crystal optical states that can be utilized can be divided into those which diffusely scatter incident light and those that alter its state of polarization. The latter require the use of a linear polarizer and analyzer. Alteration of the state of polarization has been accomplished in a uniform fashion in the art by the mechanism of field effects. However, diffuse scattering effects can be achieved by the mechanisms of field and/or current effects.
Electro-optical current effects and field effects with liquid crystalline materials are known. Speaking generally, current effects are predominantly provided by utilizing nematic liquid crystalline mesophases and mixtures of nematic and optically active materials including cholesteric mesophases. U.S. Pat. Nos. 3,592,527; 3,722,998; 3,642,348 and 3,761,172 are illustrative of diffuse scattering.
In new and growing areas of technology, new methods, apparatus, compositions, and articles of manufacture are often discovered for the application of the new technology in a new mode. The present invention relates to a new and advantageous exposure system utilizing liquid crystalline diffuse scattering effects.